keysym-utf: reject out-of-range Unicode codepoints in xkb_keysym_to_utf{8,32} It used to be UTF-8 was defined for inputs > 0x10FFFF, but nowadays that's the maximum and a codepoint is encoded up to 4 bytes, not 6. Fixes: https://github.com/xkbcommon/libxkbcommon/issues/58 Fixes: https://github.com/xkbcommon/libxkbcommon/issues/59 Reported-by: @andrecbarros Signed-off-by: Ran Benita <ran234@gmail.com>